INFLUENCE OF HYPERPOLARIZABILITIES ON NONLINEAR KERR-EFFECT RELAXATION RESPONSES

The nonlinear effects arising from the first and second hyperpolarizab ilities on the Kerr effect relaxation response of an ensemble of polar and anisotropically polarizable molecules in a strong de electric fie ld are studied by solving the infinite hierarchy of differential-recur rence relations underlying the noninertial Fokker-Planck (Smoluchowski ) equation. The step-on solution is obtained by using the matrix conti nued fraction methods. An expression for the Kerr effect relaxation ti me is derived as well following the procedure of Kalmykov, Dejardin, a nd Coffey [Phys. Rev. E 55, 2509 (1997)] which is in full agreement wi th the matrix continued fraction expression. For small values of the e lectric held, it is shown that the first hyperpolarizability contribut es to increasing the Kerr effect relaxation time while the second hype rpolarizability shifts the maximum of the relaxation time toward the l owest electric fields on increasing the value of this maximum. The dua l nature of essentially two relaxation processes is also emphasized by plotting the Kerr effect relaxation spectra for various values of the first and second hyperpolarizability parameters. (C) 1998 American In stitute of Physics.